Frequency converter



FIG. 1 is a front elevational view of a frequency converter showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a left side elevational view thereof;

FIG. 6 is a right side elevational view thereof;

FIG. 7 is a front, top and side perspective view thereof, and,

FIG. 8 is a rear, top and side view perspective view thereof. 

The ornamental design for a frequency converter, as shown and described. 